A typical calibrator of the prior art is shown in U.S. Pat. No. 4,163,938 to Moore. This patent shows a calibrator capable of generating multiple voltages or signal levels for simulating a transducer.
One of the problems experienced with prior art calibrators is associated with the remote location of a transducer relative to a recording or control device. For example, where a transducer is located near a river, an operator must first remove the transducer and attach a calibrator and then travel from the river to the site of the recording or control device, often a long distance. Once the calibrator is checked at one reference level, it is usually checked at another level characteristic of a different point in the dynamic range of the instrument. To set another level in the calibrator a trip is required back to the river to adjust the calibrator for the other signal level. The trips back and forth between the transducer and the recording or control device are time consuming in the situation where a single person is attempting calibration.
An object of the invention was to devise a calibrator which would permit a single person to calibrate a transducer or the like automatically, at multiple signal levels.